A conventional connection unit is shown in FIG. 10 and generally includes a hollow part 51 which is welded to an end of a hollow tube 50 and the hollow part 5 includes a hole 511. When connecting two hollow tubes 50 which are equipped with two respective hollow parts 51, a connector (not shown) is located between the two respective hollow parts 51 and two ends of the connector are inserted into the two respective hollow parts 51 and are positioned by two pins (not shown) extending through the connector and the two respective hollow parts 51.
However, because the hollow part 51 is welded to the hollow tube 50 so that the position of the hole 511 is not changed. This restricts the connection direction of the connector so that when assembling a frame composed of multiple hollow tubes 50 connected in different directions, the fixed position of the holes 511 restricts the shape and arrangement of the hollow tubes 50 of the assembly.
The present invention intends to provide a connection unit for connecting hollow tubes and the connection unit includes a rotatable part connected to the hollow tube so as to meet different requirements of connection.